lol @ above two replies...
guys, he wanted to know about the location of the cabin air filter. The filter is connected to the neck of the blower motor housing. It will be an easy find once u get to know about the location of the blower motor itself. Dont know much about santros myself but i'd suggest looking for a white dabba to the left of the clutch pedal assembly; if it isnt there then wait for a santro owner to reply to this thread..